1. Field of the Invention
The present invention relates to a drive for a lubrication pump for a centralized lubrication of utility vehicles, including trailers, semi-trailers, special vehicles and the like. The lubrication pump is used with lubricants which are preferably difficult to press and have a high penetration. The lubrication pump includes an agitator mounted in a lubricant container and an eccentrically driven delivery piston for the lubricant transport. The agitator and an eccentric or cam member are mounted on a common drive shaft.
2. Description of the Related Art
The preferred field of application of the present invention, i.e., a lubrication with greases which are difficult to press, concerns specifically a lubrication with greases of the class NLGI 2. These greases have a high penetration; accordingly, they require a substantial pressing force.
In the past, in a lubrication system of the above-described type, an electric motor was used as a drive. This drive acts on the common drive shaft through a step-down gear unit. The use of an electric motor has the disadvantage that because of the load-dependent variations in the rate of rotation of such an electric motor, the rate of rotation of the drive shaft drops significantly with increasing load while the rate of rotation increases with a decrease of the load.
Since the vehicles mentioned above are subjected to very different temperatures from severe frost to great heat, and since the penetration of the grease is substantially dependent upon the temperature, very different rates of rotation of the drive shaft and, thus, the delivery of different quantities of lubricant occur depending upon the prevailing temperature.
Lubrication systems used in the past have the additional disadvantage that the use of electric motors is not permitted in utility vehicles which transport dangerous material of the class A 1(GGVS UL.3/3b). While the use of explosion-protected electric motor would be theoretically possible in this danger class, this use is not possible for practical reasons because of the high manufacturing costs of such explosion-protected motors.
It is, therefore, the primary object of the present invention to provide a drive for a lubrication pump of the above-described type which can be used without additional expenses in the manufacture of utility vehicles for the dangerous material class A 1(GGVS UL.3/3b) in which the delivery rate of the lubricant is to be essentially independent of the load.